Add simple state persistence strategy

[t00ts]

Resolves: #1298

[codecov-commenter]

Codecov Report

Merging #1301 (c3a3d08) into master (828364b) will decrease coverage by 8.69%.
The diff coverage is 48.14%.

❗ Current head c3a3d08 differs from pull request most recent head 27681d1. Consider uploading reports for the commit 27681d1 to get more accurate results

@@            Coverage Diff             @@
##           master    #1301      +/-   ##
==========================================
- Coverage   50.51%   41.81%   -8.70%     
==========================================
  Files         145      144       -1     
  Lines        7544     9082    +1538     
==========================================
- Hits         3811     3798      -13     
- Misses       3066     4711    +1645     
+ Partials      667      573      -94     

Impacted Files	Coverage Δ
pkg/config/genesis/config.go	0.00% <0.00%> (ø)
pkg/core/candidate/validator.go	64.00% <ø> (+6.85%)	⬆️
pkg/core/chain/mock.go	9.09% <ø> (+0.75%)	⬆️
...nsensus/blockgenerator/candidate/blockgenerator.go	0.00% <0.00%> (-64.29%)	⬇️
...core/consensus/blockgenerator/candidate/genesis.go	0.00% <0.00%> (-69.24%)	⬇️
...kg/core/consensus/blockgenerator/candidate/mock.go	0.00% <0.00%> (ø)
...ore/consensus/blockgenerator/candidate/testutil.go	0.00% <0.00%> (-90.91%)	⬇️
pkg/core/consensus/comms.go	0.00% <0.00%> (ø)
pkg/core/consensus/fixtures.go	0.00% <0.00%> (ø)
pkg/core/consensus/header/header.go	24.50% <0.00%> (+2.41%)	⬆️
... and 187 more

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[herr-seppia]

A nit about the log

[herr-seppia]

Can you set to warn just for the first time or every n?
Otherwise it will spam the log

[t00ts]

That's kind of the idea, one should never have this value at 0. But, I get that for some random test it could be useful. I see a couple things we could do:

1. Add a "counter" member variable to Chain that helps us print "every n".
2. Have a RNG and have it print with a 20% probability...

First case I dislike, putting a member variable just for a warn print is an ugly idea. Second case I like better, but it introduces overhead. What do you think?